Phase-modulation-combination (PMC) method is researched for generation of high repetition short pulses. The method is simple and compact consisting of two photoelectric switches and two modulators, where two sub-pulses from the switches are modulated and combined interferentially, giving rise to a narrower pulse. The processes of PMC methods with different phase modulation functions are simulated numerically, and optimizations among different compression results induced by various phase function are given. Furthermore, the experimental verification for the system function is supplied, and short pulse train with 1 GHz repetition rate and 60-ps pulse duration is generated.